Japanese Patent Application Publication No. 2007-288158 (hereinafter referred to as Patent Literature 1) discloses a semiconductor device that has a diode and an IGBT (a so-called RC-IGBT). In this semiconductor device, a buffer region that has a relatively high n-type impurity concentration is provided between a cathode region and a drift region in the diode. When the diode is off, the buffer region prevents a depletion layer from extending over to the cathode region.